Prior art levering-in mechanisms for drawout switchgear include an arrangement in which a crank engages the end of a first shaft, with rotation of the first shaft being translated to rotary motion of a second shaft oriented perpendicular to the first shaft. The translating means conventionally utilizes a worm gear on the first shaft and a cooperative main gear on the second shaft. The second shaft has crank arms fixed to its ends, and rollers on the crank arms engage cradles fixed to the walls of a circuit breaker cell. Thus, when the first shaft is rotated, the second shaft is also rotated, with the rollers on the crank arms engaging the fixed cradles to either advance the circuit breaker from a disconnected position to a connected position, or from a connected position to a disconnected position, depending upon the direction of crank rotation. U.S. Pat. Nos. 3,474,201; 3,578,925; 4,002,865; and 4,017,698, which are assigned to the same assignee as the present application, all disclose levering-in mechanisms utilizing the worm-main gear drive arrangement.
Some prior art levering-in mechanisms utilize a traveling nut on the first shaft, with movement of the traveling nut being translated to movement of the circuit breaker between connected and disconnected positions. U.S. Pat. No. 3,783,209, which is assigned to the same assignee as the present application discloses a first example of a traveling nut arrangement in which a box beam on the front wall of a circuit breaker is removably fixed to the walls of a circuit breaker cell when the circuit breaker is initially positioned in the cell. A threaded shaft with a traveling nut has one end of the shaft fixed to the box beam and the circuit breaker is attached to the traveling nut. Turning the threaded shaft with a crank moves the nut and circuit breaker between connected and disconnected positions.
Another example of a traveling nut arrangement is disclosed in U.S. Pat. No. 4,112,269, which is assigned to the same assignee as the present application, with the levering-in arrangement of this patent attaching a shaft with a traveling nut to the wall of a circuit breaker cell. Turning the shaft with a crank moves the traveling nut, with the traveling nut engaging a first end of a pivotally mounted cam. The cam has a second end which engages a pin on the circuit breaker chassis, to move the circuit breaker between connected and disconnected positions.
While these prior art levering-in mechanisms function well, all require special levering-in apparatus which is costly to manufacture, assemble and adjust. Also, some circuit breakers require levering-in mechanisms and some do not, depending upon their application. In the prior art circuit breakers of which we are aware, both types of circuit breakers, those for fixed applications, and those for levering-in applications, must be manufactured and stocked, as circuit breakers of which we are aware cannot be easily modified to add levering-in, once assembled.
Thus, it would be desirable, and it is an object of the invention, to simplify the manufacturing and assembly of levering-in mechanisms. It would also be desirable, and it is another object of the invention, to be able to add a levering-in mechanism to a completed circuit breaker, making it unnecessary to manufacture and stock circuit breakers for fixed applications, and circuit breakers for levering-in applications.